Predicting new states of quantum matter is highly unlikely

Last year New Scientist published a nice article by Jon Cartwright

States of matter: The unthinkable forms beyond solid, liquid and gas

From time crystals to supersolids, we keep discovering extraordinary new kinds of matter – now the true challenge is being able to predict what we'll find next

Unlike the typical New Scientist article, this one is a measured and reasonable discussion about reality, rather than the latest wild and breathless speculations that the magazine is rife with. Unfortunately, it is behind a paywall.

I was interviewed for the article, which ends (see below) by contrasting my pessimism with the optimism of Andrei Bernevig. His optimism is based on this recent paper that reports a systematic identification of stoichiometric compounds that have topological bands and so can support topological states of matter. That is important and wonderful work. But, it is looking at what can be considered a "one-electron" problem, and so does not shake my pessimism. I do hope I am wrong.



Comments

  1. TanglawMarch 20, 2022 at 8:40 AM

    "..there could be as few as four of them [states] or perhaps thousands." I guess the number very much depends on how one defines a "state" of matter? Especially in contrast to a "phase" -- I know for example the ice/water community is actively proposing new phases, but not new states. Is there a need for sharper, more universal definitions?

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    Replies
    1. Ross H. McKenzieApril 4, 2022 at 8:46 PM

      I take "state of matter" to be the same as a "phase". It is defined by being qualitative different from other phases and there are thermodynamic singularities associated with the transition between distinct phases. Qualitative differences can be defined in terms of differences in symmetry and the types of order present.

      Chapters 1-4 of my Very Short Introduction will hopefully make this clear.

      Delete
  2. AnonymousApril 3, 2022 at 5:56 PM

    I think the optimism from A. Bernevig is based instead on this paper which catalogues and predicts materials with flat bands and most likely containing some degree of strong electron correlations. This is a bit better than the single electron picture you describe.

    What are your thoughts about this?

    https://www.nature.com/articles/s41586-022-04519-1

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    Replies
    1. Ross H. McKenzieApril 4, 2022 at 8:43 PM

      Thanks for referring me to the Nature paper that just appeared by Bernevig et al.

      That paper makes NO predictions of new states of matter. It just identifies materials that would be interesting to study because they may exhibit interesting states of matter.
      Again, it is just looking at band structures, which I would still say are in essence a "one-electron" picture.

      This work is interesting and worthwhile. But, it is not predicting new states of matter.

      Delete

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